[sedge]

Jeffac
Looks like your having a lot of fun .I  had a look at a few sites on the net ,there?s a good one on audio karma [using piezo tweeters wisely a how to] all you need to know to set up a piezo properly and protect your amp from hf instability .I got a little excited reading all this but then thought hold on a sec I don?t feel I need any more hf.
I have had piezo tweeters for many years but last year some nice person decided  to set fire to my car  along with my piezos ,if I still had them I?d definitely  give it a go .
For the last few weeks I have been side tracked once again from my  hard foam panels,this time it is an ali panel [did I just hear a groan?] I had tested the panel a long time ago but the sheets were too thin [made a horrible sound but in the sun light they looked just like those 3D nxt animations on the web ] bouncing all over the place .
Then I decided to glue card to the back ,this helped to dampen it a little and sounded quite good ,then I thought what if I glued two of the metal sheets together.
I was a little disappointed when I tapped the panel and it sounded quite dead .
It is still quite flexible [you can do a good impersonation of Rolf Harris?s tie my kangaroo down sport    ] [all together now  ]
But when I hooked up an exciter to it ,it sounded very good ,not dull as expected .
The panel seems to be self damping [no ringing ]and has a very natural sound .
The low fr is not as good as the smaller hard panels but give good response from about 200 hz up to 20k [the test  panel is 77cm x98cm ] three sheets look to be less than 1ml ,my eyes are not that good anymore
I am going to have to get my pal over to have a listen and sea what he thinks.
Until then [all together now  ]
sedge

[jeffac]

Hi Sledge,

Thanks for the links on piezo's and updates, and yep, I'm having a bit of fun, learning a little and marking time "just in case" someome discovers THE magic panel material in the next little while that in addition to making perfect sound, can be recycled and is essentially given away.  More like ..."Tell him he's dreamin". 

The father of a mate of one of my sons is a professional signwriter, I might see whether he's used 2 mm Dibond/Dilite before and can get me some to test. It looks the right kind of material and apparently tests well. Still, I kind of like the idea of wood-based materials like Luxcell on Gatorfoam or cardboard-type boards .... sticking to the 'mother-of-tone' principles that appropriately stiffened with natural resins, these have the potential to generate very natural tone. Might end up going Gatorfoam, as I think married with a piezo cone (maybe in the centre, maybe at the edge  as Ziggy has played with), that this could nicely fill in any missing HF. The other thing that I've noted, because the piezo plays well down into the upper mids, and sounds lightning fast to me, is that this aids dymanics and instruement attack and musical aliveness (starting to repeat myself now  ). Soorrrry, its just me..... but the last thing that want from this project is a laid back smooth sound. If its got the potential to smack me the face with natural and live-like dynamics, smack away.   aa

cheers.. jeffac

[captainjack115]

aa...........O.K..............HERE WE GO...................the Re-board rep will visit me at work on a business and private

What's Re-Board?

I couldn't Google it. Can I get it in the U.S.?

Still using 20 X 30 inch foamboard, the highs are great and the lows into lower 30's.
I have two prototypes, one set has one exciter with square corners. The second set has two exciters and rounded corners. The seconded set sounds much better, a fuller sound with lots of volume.

Whether one exciter or two, the panels have a native resonance around 30 Hertz.
I would think that a larger panel would lower resonance, adding more exciter will change things. With conventional dynamic drivers, the Fs can be lowered by adding weight to the cone.

I have lots of exciters. Imagine having 16 or 32 exciters per panel? I don't know if it will play good, but it will play louder than I'll ever be able to stand.

Jack

[usp1]

I went back and tried several exciter combinations. It seems two gives me the best results on white gatorfoam 2'x4' panels. Reasonably good SPL...I am using a bigger amp and it seems to work well with it.

[j gale]

Zygadr,  Don't think a little warping matters at all. Corners probably should be rounded off an that would probably minimize warping. Unless it is bad enough to pull exciters off who cares?

[j gale]

Gatorfoam tech bulletin says it will flatten out if temperature is equal on both sides. If your panel was face down on the floor for long enough to have that temp difference that would explain the warp. Stand it up or lay on side for awhile should bring it back to pretty flat.

[usp1]

The length of the panel, the load of the exciters in the middle and resting it against the wall probably caused it to curve lengthwise. I think a panel that large needs to be held in a frame to avod the inevitable pull of gravity.

[zobsky]

Gatorfoam is most likely better suited to much smaller panels only?

Let's face it........Gatorfoam sounds great, but picking up a sheet that's 78inches by 28 inches by one end and levering it in to an upright position, watching it bend like a banana in the middle is asking for trouble........I should have known better ............it's just not rigid enough at that size.
Maybe 10mm would have been better..........but I doubt it

Regardless of whether your panels regain their shape or not, how would they react if they were sawn in two i.e. from one 78" x 28" panel to two 39" x 28" panels per channel (each with half the original number of exciters). The stress placed on each panel would be less. From a pure open baffle perspective, there shouldn't be much roll off in bass since the minimum dimension (28") still remains the same.

I haven't any gatorboard yet that I can play with, and am not suggesting that you cut up your panels, ..but wanted some practical observations.

Also, FWIW, I compared my original sonic impact/NXT transducer with one of the Parts Express buyout transducers. The buyout transducer is a bit beefier, seems more efficient and seems to have more bandwidth, both lower down and in the treble.

[el`Ol]

Hello,
I'm going to copy the podium system.
So i need some information about the materials used in that setup.
I know there is a honeycomb panel made of Nomex but i'm wondering about the thickness...
then there is a mylar sandwich protecting the nomex honeycomb right?
even here i wish to know the thickness of the mylar.
I do not want to seem arrogant cause of this  you guys are fantastic and you are working well, very well.
I'm learning a lot from your mistakes and your successes, but I would overcome this stage and use the finest materials to get as close as possible to a hi-end results.
many thanks to all

p.s.
clearly once assembled the panel, will explore the position of the exciters!

Here is an Italian company that manufactures both the nomex honeycomb and a very interesting material called Monocore 3D. To get enough HF the panel shouldn't have much more than 500g/m^2. The 1000g/m^2 of the 5mm Gatorfoam is already a bit much.
http://www.metalleido.com/index_E.htm

[captainjack115]

UPDATE :

The Re-board rep. will be seeing me tomorrow, 9.15 am Perth time here at my office.

As soon as the meeting, examination of the samples are over, I will report to this forum immediately on my findings and observations.

[/b]

Ziggy, I know you had a bit of trama going on with the Gatorboard, but I'd really like to know more about Re-Board. Googling doesn't tell me what I want to know.

Jack

[j gale]

You can't leave us hanging

[usp1]

Ziggy.... stop teasing

[Copperhead]

Ziggy,  why are you looking at the 10mm sample? At 2kg/m2 it's too heavy. The 5mm is a little lighter than the Gatorfoam, wouldn't that be the
logical choice?

[zobsky]

For what its worth, ... last week, I called a couple local sign makers. One of them didn't use gatorfoam anymore , but had transitioned to using something called "UltraBoard", .. apparantly expanded polystyrene with solid polystyrene faces. I wonder if this is equivalent to Forex board. He wouldn't give me samples / scrap, .. said I had to buy it. Maybe I'll go in person when I have a day off.

I haven't been able to find density or rigidity specs for it though.

http://www.artsupply.com/foamcore/ultraboard.htm

[captainjack115]

I haven't gone back through all the pages of this thread, but I have a question.

Has anyone here actually looked into NXT licensing? If it's not outrageously expensive, I may be interested in using their technology and software for commercial use. Nothing "Big Time", just a cottage industry sort of thing.

By the way, I designed and built my own exciter. My design is not a coil of wire fastened to a bobbin. I used a series of spaced aluminum conductors on the face of the panel and a magnetic assembly on the back side. The magnets (a lot of them) are properly polarized and placed near the panel. The good part is, high frequencies are excellent and well beyond 20,000 Hertz.
The bad part is low efficiency and the expense of the magnets. Not to mention the weight.

Project scrapped!

Jack   

[captainjack115]

Yet another question!

I decided to go directly to the NXT site and do their "Contact Us" Email. Minutes later I received a failure notice that there was no legitimate address for me to contact.

Has anyone else had this problem?

Jack

[zobsky]

We need to be careful that "cleaner/crisper" isn't really "harsher" in disguise. Looking forward to your long term impressions, esp. those with larger panels.

If you're concerned about your forex board not being rigid enough, you might be able to address that by ripping a long thin strip of the same (say 1" or so) and gluing it on edge lengthwise to the main panel. Instant stiffening.

Lastly, do you have the means to measure impedance of your various boards? That should tell us a bit (though not the whole picture) about the bass response with various materials. I use ARTA and my PC sound card and a rig made up of a couple of dollars of parts.
http://zobsky.blogspot.com/2008/01/simple-loudspeaker-measurement-jig-for.html

[jeffac]

zobsky,

Very clear "how to" instructions, you a teacher  , and "overall impedance" of multiple exciters/piezos on a large panel would be very interesting to measure assuming that this can be done as for a single driver.  An extra rib added to the vertical panel edge is something I've thought to too, and for large corrugated cardboard sheets that have started to sag, placing sharp bends vertically along a corrugation to generate a wings, that can be bent back a whatever angle sounds right, also straightens the panel front nicely.

Next play panels will be 120 x 75 cm 4 mm corrugated cardboard with 4 PE exciters per panel variably spaced, small wings on each side leaving ~50 cm front panel width minus the wings. Keen to through-panel mount a piezo tweeter cone too, as I love their added bite  aa, but will test without initially to see whether that "YES" moment happens again.

cheers.. jeffac

[jeffac]

Ziggy, all good mate,

Don't feel as though you're letting anybody down here. From the very start its been clear that you've been over the moon with the sound produced from your large Gatorfoam panels, so much so that you wanted to share this, and any issues with HF extension have been solved well enough by your piezo cone experiments. And agreed I'd be much more weary of hacking holes to surface mount piezo cones on something like Gatorfoam that I paid for. Still might though if my experiments with cardboard continue to go well.

TBH I was set to go with Gatorfoam ages ago except for HF roll-off reports followed by the "potential" of finding THE cheap panel matertial with cosmic HF qualities. And it might still be found by one of us here willing to find interesting stuff and test it.

Speaking of which  aa, and seeing I have these large-ish cardboard sheets, I thought I should test stiffening more seriously.  Having a 4 L tin of Tung Oil floorguard laqeur left over from floorboard polishing, I'm having a play with this. Not ideal probably for mother-of-tone TONE, but good enough to test. Diluted 1:1 with turps so like water consistency, I ran this into the cardboard corrugations until I could see it soaking through the cardboard surface sheet on either side. On a small 30 x 30 cm test sheet, no probs getting good saturation. Then liberally coated each outer surface and let dry overnight and during yesterday. Results of scratch, fingernail ping and finger pong tests, very interesting.  aa

Scratch: noticeably louder and significantly crisper
Fingernail Ping: sharper more dynamic crack; with my ear near the surface, I think doing this a few times has caused hearing damage 
Finger pong: the tom-tom like hollow-sounding resonance of the untreated sheet is almost completely damped on the treated sheet and replaced by something higher in pitch but without the lingering hollow sounding resonance
Strength: generally better and the cardboard is more resistant to twisting.

Conclusion: Based on ideal panel characteristics. I think. Certainly there are enough positives here from treating cardboard with a stiffener to test this with the larger panels. Could be a disaster trying to similarly coat the big sheets but could transform them to something magic aa, you never know. Will keep you posted.

cheers.. jeffac

[Donka]

OH how times have changed.

Adding Piezo's

new panel materials

cutting holes

actually measuring.

Why would you do that?  My gatorfoam panels are